ABSTRACT Four conodont biozones, including three subzones, are interpreted within a revised lithostratigraphic framework for the upper Boone Group and Mayes Group in northeastern Oklahoma and adjacent parts of Missouri, Kansas, and Arkansas. Although revised lithostratigraphy is principally based on observed lithologic characteristics and stratigraphic relationships, conodont biostratigraphic data played an important role in correlation and final organization of units. Within the upper Boone Group, Biozone 1 (lower Meramecian) includes the Ritchey Formation and the Tahlequah limestone and Biozone 2 (middle Meramecian) includes the Moccasin Bend Formation and Quapaw Limestone. The Mayes Group spans Biozone 3 and Biozone 4. Biozone 3 (upper Meramecian) is represented by the Bayou Manard Member of the Pryor Creek Formation (new name). Biozone 4 marks the appearance of definitive Chesterian conodont fauna. The lower two subzones within Biozone 4 correspond to the Lindsey Bridge (Biozone 4L) and Ordnance Plant (Biozone 4M) members of the Pryor Creek Formation, whereas the upper subzone consists of the Hindsville Formation (Biozone 4U). Documentation of conodont taxa and recognition of the proposed biozones provides relative time constraints for genetically meaningful interpretations of regional geology and subsequent evaluation of the Mayes Group and upper Boone Group within a broader interregional context.